[Eeyore[_2_]]

wrote:

Hello Everyone,

I am looking for a Greybeard of sorts. I have recently been thrown
into the audio realm, particularly testing with semiconductor PA's,
and I am curious to know where the 600 ohm impedance originated from.

Telegraph wires.

Graham

[[email protected]]

Hello Everyone,

I am looking for a Greybeard of sorts. I have recently been thrown
into the audio realm, particularly testing with semiconductor PA's,
and I am curious to know where the 600 ohm impedance originated from.
For example, most testing I have done is with 4 ohm to 8 ohms with
PA's and 16 ohms or 32 ohms with headphones for portable audio
(computing, MP3, cell phone) and there is generally no need for
impedance matching.
I have managed to piece together some basic information from multiple
Google searches that 600 ohms originated from the POTS and was adopted
by the pro audio crowd decades ago, but I would like some more
'historical' information of when, why, and how.
What prompted this question is that another group uses an HP 8903B
which has either a 50 ohm or 600 ohm impedance to test audio analog
CMOS switches and 600 ohms is selected for THD+N measurements.
The philosophy of the impedance difference intrigued me and thus has
lead me on a search to understand where the 600 ohms standard came
from and why some equipment only has this option.
Any tips, notes, or thoughts will be greatly appreciated.

[David Gravereaux]

wrote:
Hello Everyone,

I am looking for a Greybeard of sorts. I have recently been thrown
into the audio realm, particularly testing with semiconductor PA's,
and I am curious to know where the 600 ohm impedance originated from.

An old telephone standard.

For example, most testing I have done is with 4 ohm to 8 ohms with
PA's and 16 ohms or 32 ohms with headphones for portable audio
(computing, MP3, cell phone) and there is generally no need for
impedance matching.

A more correct term might be power matching. When you have a device
with an output impedance, such as the plate of an electron tube, it
becomes important to match the impedances so that you get greatest power
transfer. Best power transfer is when output impedance matches input
impedance. The drawback is that half the voltage is lost. Search on
the term "Thevenin's equivalent".

I have managed to piece together some basic information from multiple
Google searches that 600 ohms originated from the POTS and was adopted
by the pro audio crowd decades ago, but I would like some more
'historical' information of when, why, and how.

Correct and I don't know the details.

What prompted this question is that another group uses an HP 8903B
which has either a 50 ohm or 600 ohm impedance to test audio analog
CMOS switches and 600 ohms is selected for THD+N measurements.
The philosophy of the impedance difference intrigued me and thus has
lead me on a search to understand where the 600 ohms standard came
from and why some equipment only has this option.
Any tips, notes, or thoughts will be greatly appreciated.

Apply Thevenin's equivalent on a circuit with a 50 ohm output impedance
and a 10K input impedance and things look a whole lot different. As the
load is greater than ten times the output, that system is called 'equal
voltage transfer' as opposed to a power matched system.

[Don Pearce[_3_]]

On Sun, 24 May 2009 14:32:39 -0700, David Gravereaux
wrote:

wrote:
Hello Everyone,

I am looking for a Greybeard of sorts. I have recently been thrown
into the audio realm, particularly testing with semiconductor PA's,
and I am curious to know where the 600 ohm impedance originated from.

An old telephone standard.

For example, most testing I have done is with 4 ohm to 8 ohms with
PA's and 16 ohms or 32 ohms with headphones for portable audio
(computing, MP3, cell phone) and there is generally no need for
impedance matching.

A more correct term might be power matching. When you have a device
with an output impedance, such as the plate of an electron tube, it
becomes important to match the impedances so that you get greatest power
transfer. Best power transfer is when output impedance matches input
impedance. The drawback is that half the voltage is lost. Search on
the term "Thevenin's equivalent".

I have managed to piece together some basic information from multiple
Google searches that 600 ohms originated from the POTS and was adopted
by the pro audio crowd decades ago, but I would like some more
'historical' information of when, why, and how.

Correct and I don't know the details.


The matched 600 ohm lines are important for phones because the lines
are so long. When the load is mismatched power bounces and reflects
back the way it came. the result with a cable that stretches across a
country is an echo, which is mighty off-putting. So a minimum matching
standard was imposed, which restricted the amplitude of echoes to an
acceptable level. On long lines echo becomes a problem long before any
mismatch power loss matters.

d

[Chris Hornbeck]

On Sun, 24 May 2009 13:42:20 -0700 (PDT), wrote:

I am curious to know where the 600 ohm impedance originated from.

Others here will have better detail, but it's the "characteristic
impedance" of conductors spaced a couple inches apart in free air.

Characteristic impedance is the resistive value that an infinitely
long line would look like. Another way to describe it is that it's
the resistive load applied to that not-infinitely-long line that makes
it look like a resistor (and, of that value).

All the best fortune,
Chris Hornbeck

[Chris Hornbeck]

On Sun, 24 May 2009 17:56:34 -0400, "Soundhaspriority"
wrote:

Good point, it's "ladder line", http://en.wikipedia.org/wiki/Ladder_line .

But since telephony audio was never transmitted over ladder line, it seems
they picked 600 ohms as a standard audio impedance simply because it was a
number they knew.

Two conductors in free air with an occasional spacer at a coupla
inches is about 600 Ohms.

It wasn't so much arbitrarily chosen as mandated by fundamentals.
Kinda like the World is 73 Ohms, but different!


Much thanks, as always,
Chris Hornbeck

[Richard Crowley]

"Soundhaspriority" wrote ...
OK, correct me on this. Way back when, did they actually transmit long
distance audio telephony over ladder line? Perhaps they did, before they
developed effective insulation.

Bare conductors spaced a few inches apart and hung from
*telephone poles*. That was the technology for long-distance
lines back before plastic-insulated multi-conductor cable came
into use. At audio frequencies (vs. RF) it is essentially "ladder-
line" and had the 600-ohm characteristic impedance.

But more fascinating to me is the technique I saw implemented
for miles and miles out in the Mojave desert (and similar desolate
places in S.Calif.) They sent RF over single bare conductors
(like old telephone lines). But instead of just a big glass insulator
on the utility pole, there would be a pair of "funnels" back to back
so that the RF field was "funneled" down to effectively a short
(a few inches) length of "coaxial cable" and then back out to the
bare conductor in air. I thought it was called "G line" or something,
but casual Googling didn't reveal anything.

[David Ballinger]

"Soundhaspriority" wrote in message
...

"Chris Hornbeck" wrote in message
...
On Sun, 24 May 2009 17:56:34 -0400, "Soundhaspriority"
wrote:

Good point, it's "ladder line", http://en.wikipedia.org/wiki/Ladder_line
.

But since telephony audio was never transmitted over ladder line, it
seems
they picked 600 ohms as a standard audio impedance simply because it was
a
number they knew.

Two conductors in free air with an occasional spacer at a coupla
inches is about 600 Ohms.

It wasn't so much arbitrarily chosen as mandated by fundamentals.
Kinda like the World is 73 Ohms, but different!


Much thanks, as always,
Chris Hornbeck
----------------------------------------------------------------------------
OK, correct me on this. Way back when, did they actually transmit long
distance audio telephony over ladder line? Perhaps they did, before they
developed effective insulation.

Bob Morein
(310) 237-6511

Yes I have a gray beard, Nobody here remembers when telephone poles had
cross arms with green or clear glass insulators, yes open wire pairs, multi
pair cable hadn't been perfected yet, the last few places that used open
wire were the railroads for signals and com. the phone company started
frequency multiplexing on open wire lines 12 channels on 2 pairs just in
time for WWII. we have come a long way in a short time, not everybody had
telephones back then usually the rich and the Doctor and the sheriff, had 8
party lines too. Very few trunk lines between cities, it would take hours
to set up a long distance call, some of the little companies didn't talk to
each other at all. It wasn't exactly ladder line but the wires were
stretched tight enough they never crossed and stayed equidistant,
occasionally there would be a mid span cross-over device to minimize
crosstalk on the multiplex. I started with Bell Tel in 1970, my observation,
new technology is built on old, you have a system of standards in place that
works and everyone has in common. All of our program audio ckts were 600
ohms, all of the test sets were 600, 900, or 1200 ohm impedance, for 19 or
22 or 24 or 26 gauge wire. When I was in the Navy I noticed the military had
an affinity for 500 ohm ckts ?? another convention. For Bell it was all
defined in the Bell System Practice, It said what and how and how often, if
you didn't follow the practice you could get a day off or fired. 0 dbm at 1
kHz into 600 ohms = 1 milliwat, I'm not going to complain it works for me.
Best regards,
David____________

[Don Pearce[_3_]]

On Sun, 24 May 2009 16:38:44 -0700, "Richard Crowley"
wrote:

"Soundhaspriority" wrote ...
OK, correct me on this. Way back when, did they actually transmit long
distance audio telephony over ladder line? Perhaps they did, before they
developed effective insulation.

Bare conductors spaced a few inches apart and hung from
*telephone poles*. That was the technology for long-distance
lines back before plastic-insulated multi-conductor cable came
into use. At audio frequencies (vs. RF) it is essentially "ladder-
line" and had the 600-ohm characteristic impedance.

But more fascinating to me is the technique I saw implemented
for miles and miles out in the Mojave desert (and similar desolate
places in S.Calif.) They sent RF over single bare conductors
(like old telephone lines). But instead of just a big glass insulator
on the utility pole, there would be a pair of "funnels" back to back
so that the RF field was "funneled" down to effectively a short
(a few inches) length of "coaxial cable" and then back out to the
bare conductor in air. I thought it was called "G line" or something,
but casual Googling didn't reveal anything.


That's actually a waveguide mode - can't remember the designation
either, but it needs to be launched by those funnels (actually quarter
wave matching transformers). The wire is only used for guiding, and
all the actual power transfer is done in the surrounding air, so the
loss is extremely small - many miles of transmission are easily
possible.

Any normal two conductor system uses transverse electromagnetic mode,
which is the same as the radio wave that propagates in free air, and
relies on current in the conductor in quadrature to the surrounding
magnetic field (TEM). The single conductor mode either has no magnetic
component so is probably TE1, or no electric component, so is TM1).

d

[Don Pearce[_3_]]

On Sun, 24 May 2009 21:35:09 -0400, "Soundhaspriority"
wrote:


"Don Pearce" wrote in message
news:4a25e7d3.662406234@localhost...
On Sun, 24 May 2009 16:38:44 -0700, "Richard Crowley"
wrote:

[snip]

Any normal two conductor system uses transverse electromagnetic mode,
which is the same as the radio wave that propagates in free air, and
relies on current in the conductor in quadrature to the surrounding
magnetic field (TEM). The single conductor mode either has no magnetic
component so is probably TE1, or no electric component, so is TM1).

d

Don, I would dispute that. The wire is a guide for a surface wave. Surface
waves are mixed mode.

This is all a long time ago, and I've been trying to find my reference
books - I remember doing experiments with it back in university (1971
ish). I really can't remember this being a mixed mode propagation,
though.

d

[Don Pearce[_3_]]

On Sun, 24 May 2009 22:15:19 -0400, "Soundhaspriority"
wrote:


"Don Pearce" wrote in message
news:4a26f8ac.666714421@localhost...
On Sun, 24 May 2009 21:35:09 -0400, "Soundhaspriority"
wrote:


"Don Pearce" wrote in message
news:4a25e7d3.662406234@localhost...
On Sun, 24 May 2009 16:38:44 -0700, "Richard Crowley"
wrote:

[snip]

Any normal two conductor system uses transverse electromagnetic mode,
which is the same as the radio wave that propagates in free air, and
relies on current in the conductor in quadrature to the surrounding
magnetic field (TEM). The single conductor mode either has no magnetic
component so is probably TE1, or no electric component, so is TM1).

d

Don, I would dispute that. The wire is a guide for a surface wave. Surface
waves are mixed mode.

This is all a long time ago, and I've been trying to find my reference
books - I remember doing experiments with it back in university (1971
ish). I really can't remember this being a mixed mode propagation,
though.

d

Don, you can read about it he http://www.corridor.biz/parts123.pdf
As far as the books, I have the same problem. I've had seven graduate course
in E-M theory, but do I really want to work the texts just to win an
argument with you?


No more than I do, I'm sure - this isn't a contest after all, just
sharing some dim and distant memories.

d

[Don Pearce[_3_]]

On Sun, 24 May 2009 22:15:19 -0400, "Soundhaspriority"
wrote:


"Don Pearce" wrote in message
news:4a26f8ac.666714421@localhost...
On Sun, 24 May 2009 21:35:09 -0400, "Soundhaspriority"
wrote:


"Don Pearce" wrote in message
news:4a25e7d3.662406234@localhost...
On Sun, 24 May 2009 16:38:44 -0700, "Richard Crowley"
wrote:

[snip]

Any normal two conductor system uses transverse electromagnetic mode,
which is the same as the radio wave that propagates in free air, and
relies on current in the conductor in quadrature to the surrounding
magnetic field (TEM). The single conductor mode either has no magnetic
component so is probably TE1, or no electric component, so is TM1).

d

Don, I would dispute that. The wire is a guide for a surface wave. Surface
waves are mixed mode.

This is all a long time ago, and I've been trying to find my reference
books - I remember doing experiments with it back in university (1971
ish). I really can't remember this being a mixed mode propagation,
though.

d

Don, you can read about it he http://www.corridor.biz/parts123.pdf
As far as the books, I have the same problem. I've had seven graduate course
in E-M theory, but do I really want to work the texts just to win an
argument with you?

A quick read suggests that the line is indeed TM, but with a
considerable evanescent region of TEM at the start and finish, so yes,
very mixed mode towards the ends of the line.

d

[[email protected]]

Thank you all for the replies. The information about the "ladder
line" for audio across telephone lines being 600 ohms looks like the
answer I was looking for. I am also going to look through the Bell
Systems Technical Journal (great find and thanks!) for the actual
papers discussing telephony.

[Paul Stamler[_2_]]

wrote in message
...
I have managed to piece together some basic information from multiple
Google searches that 600 ohms originated from the POTS and was adopted
by the pro audio crowd decades ago

Actually, at the time the standard was adopted, the pro audio crowd *was*
the POTS people, at least as far as electrical stuff was concerned. Nobody
but the phone company was doing electrical things with audio. The phonograph
recording world was entirely acoustical.

Later on folk began messing with electrical audio for other things, like
sound films, radio broadcasting and recordings. Much of that work was done
by Western Electric and Bell Labs, both branches of the monopoly AT&T,
better known as Bell Telephone Co..

A lot of audio equipment adhered to the phone company standard because it
had to; radio stations, for example, linked master control to the
transmitter by leased phone lines, so the consoles that drove the lines had
to match the telco standard, and so did the inputs to the transmitters at
the station. It was possible to make gear for internal studio use which
wasn't telco-compatible, but practically nobody did, because that would
limit its applicability, particularly if the station's console was all 600
ohm in and out for telco compatibility.

It was really the 1970s before pro equipment began to be built to a
different standard.

Peace,
Paul

[Trevor Wilson]

"Eeyore" wrote in message
...


wrote:

Hello Everyone,

I am looking for a Greybeard of sorts. I have recently been thrown
into the audio realm, particularly testing with semiconductor PA's,
and I am curious to know where the 600 ohm impedance originated from.

Telegraph wires.

Graham

**I dunno if your emails are bouncing or not. Can you send another please?


--
Trevor Wilson
www.rageaudio.com.au

[Scott Dorsey]

In article ,
wrote:
Hello Everyone,

I am looking for a Greybeard of sorts. I have recently been thrown
into the audio realm, particularly testing with semiconductor PA's,
and I am curious to know where the 600 ohm impedance originated from.

If you have open-wire transmission lines with two 18 ga. wires about
five inches apart on the telephone pole, you have a line with a 600
ohm characteristic impedance. This was the standard telephone circuit
well into the 1920s, and as a result the phone company adopted 600 ohm
lines and termination for almost everything.

A sidelight: 20 ga twisted pair with thick cotton insulation tends to
be around 150 ohms characteristic, so the phone company also used that
as a standard, starting in the teens. For many years, CBS Radio used
150 ohms as their transmission line standards, so their equipment would
not interoperate with the rest of the industry without adding more
matching transformers. A lot of gear still had 150 ohm taps well into
the seventies.

For example, most testing I have done is with 4 ohm to 8 ohms with
PA's and 16 ohms or 32 ohms with headphones for portable audio
(computing, MP3, cell phone) and there is generally no need for
impedance matching.

Right, in the modern world almost everything has a high-Z input and a
low-Z output, and you don't care about the cable characteristic impedance
unless you are running cables for tens of miles (as the telcos do).

I have managed to piece together some basic information from multiple
Google searches that 600 ohms originated from the POTS and was adopted
by the pro audio crowd decades ago, but I would like some more
'historical' information of when, why, and how.
What prompted this question is that another group uses an HP 8903B
which has either a 50 ohm or 600 ohm impedance to test audio analog
CMOS switches and 600 ohms is selected for THD+N measurements.
The philosophy of the impedance difference intrigued me and thus has
lead me on a search to understand where the 600 ohms standard came
from and why some equipment only has this option.
Any tips, notes, or thoughts will be greatly appreciated.

You want goofy, look up where the 50 and 75 ohm transmission line
standards came from...
--scott

--
"C'est un Nagra. C'est suisse, et tres, tres precis."

[mcdonaldREMOVE TO ACTUALLY REACH [email protected]]

Scott Dorsey wrote:


You want goofy, look up where the 50 and 75 ohm transmission line
standards came from...


That's not goofy. The impedance of free space is (about) 75 ohms, as
is, not accidentally, the impedance of a matched dipole antenna.

The minimum loss of a coaxial transmission line with air insulation
occurs at 75 ohms (for the same reason!) while the minimum
loss for a coax line with plain polyethylene insulation is at
50 ohms approximately. Foam insulation line is intermediate.

It is a pain in the butt that TV (cable and receiving antennas) uses 75 ohm
lines while almost all other RF electronics equipment is 50 ohm.

Doug McDonald

[Don Pearce[_3_]]

On Mon, 25 May 2009 11:40:48 -0500, "mcdonaldREMOVE TO ACTUALLY REACH
wrote:

Scott Dorsey wrote:


You want goofy, look up where the 50 and 75 ohm transmission line
standards came from...


That's not goofy. The impedance of free space is (about) 75 ohms, as
is, not accidentally, the impedance of a matched dipole antenna.


The impedance of free space is 377 ohms (120 pi)

The minimum loss of a coaxial transmission line with air insulation
occurs at 75 ohms (for the same reason!) while the minimum
loss for a coax line with plain polyethylene insulation is at
50 ohms approximately. Foam insulation line is intermediate.

Minimum loss (at which copper loss and dielectric loss cross) comes at
about 67 ohms. There are cables at that impedance, but I've never seen
one.

It is a pain in the butt that TV (cable and receiving antennas) uses 75 ohm
lines while almost all other RF electronics equipment is 50 ohm.


Very true.

d

[mcdonaldREMOVE TO ACTUALLY REACH [email protected]]

Don Pearce wrote:
On Mon, 25 May 2009 11:40:48 -0500, "mcdonaldREMOVE TO ACTUALLY REACH
wrote:

Scott Dorsey wrote:

You want goofy, look up where the 50 and 75 ohm transmission line
standards came from...

That's not goofy. The impedance of free space is (about) 75 ohms, as
is, not accidentally, the impedance of a matched dipole antenna.


The impedance of free space is 377 ohms (120 pi)

You are of course right! I had a brain lapse! I was equating FOLDED
dipole to plain dipole. It's bad getting old!


Minimum loss (at which copper loss and dielectric loss cross) comes at
about 67 ohms. There are cables at that impedance, but I've never seen
one.




I've actually used them. I've also used the 125 ohm lines,
and even 250 ohm rigid ones (with teensy inner conductor held
in place with nylon fishing line.

Doug McDonald

Doug McDonald

[[email protected]]

Minimum loss (at which copper loss and dielectric loss cross) comes at
about 67 ohms. There are cables at that impedance, but I've never seen
one.


Copper loss dominates at frequencies below about 1 GHz for most
standard cables.

For a given outer diameter Foam cable has lower loss because the lower
dielectric constant allows the cable to have a larger center conductor
therefore reducing the copper loss. It is not because the dielectric
losses are lower. This is a common misconception.

Dielectric losses are not an issue for most cables below microwave
frequencies.

http://www.epanorama.net/documents/w...impedance.html

Mark

[[email protected]]

Anyone who goes this far with a nontechnical audio audience is
showing off how big and thick his dick is. It is not necessary to
really understand transmission line theory in audio (unless you are
the phone company). Explaining the principle of common vs.
differential mode is enough.

[isw]

In article ,
"mcdonaldREMOVE TO ACTUALLY REACH wrote:

Scott Dorsey wrote:


You want goofy, look up where the 50 and 75 ohm transmission line
standards came from...


That's not goofy. The impedance of free space is (about) 75 ohms, as
is, not accidentally, the impedance of a matched dipole antenna.

The minimum loss of a coaxial transmission line with air insulation
occurs at 75 ohms (for the same reason!) while the minimum
loss for a coax line with plain polyethylene insulation is at
50 ohms approximately. Foam insulation line is intermediate.

75 ohms answers the question "what impedance has the lowest attenuation
per unit length for a given outside diameter?". I believe that is true
*regardless* of the dielectric.

The fact that 75 ohms (and 300 ohms) are antenna impedances is
convenient, but not the main reason for the prevalence of 75 ohm cable
-- the preponderance of antennas are vertical quarter-wave devices, and
those run around 50 ohms.

50 ohms (sort of) answers the question "what impedance has the greatest
power handling capacity for a given outer diameter?". I believe that is
true *regardless* of the dielectric.

The precise answer is around 37 ohms, but the curve is very broad, and
50 (or 51.5 or 52) ohms is useful for (vertical) antennas, so that's the
impedance cable is built to. Incidentally, the lower DC resistance of 50
ohm cable made it the best choice for Ethernet (over 75 ohm's lower
attenuation) because it makes collision detection work better.
Propagation delay limits the length of an Ethernet segment anyhow, and
that doesn't vary greatly with impedance.

It is a pain in the butt that TV (cable and receiving antennas) uses 75 ohm
lines while almost all other RF electronics equipment is 50 ohm.

I suspect that the length of coax in use for cable TV RF plus baseband
video far, far exceeds all other uses of any other impedance of cable,
and in those uses, low transmission loss is more important that anything
else. Plus, of course, the major antenna type used for TV is the
(folded) dipole, which, at 300 ohms, has an impedance that is
"convenient" for use with 75 ohm coax.

Isaac

[Richard Crowley]

wrote from Gooooooooogle Groups ...
Anyone who goes this far with a nontechnical audio audience is
showing off how big and thick his dick is. It is not necessary to
really understand transmission line theory in audio (unless you are
the phone company). Explaining the principle of common vs.
differential mode is enough.

You completely missed both the content and the intent of the
question. But thanks for playing. Shoulda known that this sort
of garbage slops over from r.a.o

[[email protected]]

On May 24, 11:09*pm, "Paul Stamler" wrote:
wrote in message

...

I have managed to piece together some basic information from multiple
Google searches that 600 ohms originated from the POTS and was adopted
by the pro audio crowd decades ago

Actually, at the time the standard was adopted, the pro audio crowd *was*
the POTS people, at least as far as electrical stuff was concerned. Nobody
but the phone company was doing electrical things with audio. The phonograph
recording world was entirely acoustical.

Later on folk began messing with electrical audio for other things, like
sound films, radio broadcasting and recordings. Much of that work was done
by Western Electric and Bell Labs, both branches of the monopoly AT&T,
better known as Bell Telephone Co..

A lot of audio equipment adhered to the phone company standard because it
had to; radio stations, for example, linked master control to the
transmitter by leased phone lines, so the consoles that drove the lines had
to match the telco standard, and so did the inputs to the transmitters at
the station. It was possible to make gear for internal studio use which
wasn't telco-compatible, but practically nobody did, because that would
limit its applicability, particularly if the station's console was all 600
ohm in and out for telco compatibility.

It was really the 1970s before pro equipment began to be built to a
different standard.

Peace,
Paul

This is a shame that a golden information like this is not
documented. I get the feeling that there are many people who know the
history but have never put it in pen form. I am not lucky enough to
work under a greybeard mentor who not only knows the electrical
aspects of audio, but also knows the reasons behind the way things are
done. As the older generation retires there is certainly lots of
knowledge that goes along with them.

[Scott Dorsey]

In article ,
wrote:
Anyone who goes this far with a nontechnical audio audience is
showing off how big and thick his dick is. It is not necessary to
really understand transmission line theory in audio (unless you are
the phone company). Explaining the principle of common vs.
differential mode is enough.

I'm not sure I understand what a "nontechnical audio audience" is. Audio
is necessarily a technical field.
--scott
--
"C'est un Nagra. C'est suisse, et tres, tres precis."

[Scott Dorsey]

wrote:
This is a shame that a golden information like this is not
documented. I get the feeling that there are many people who know the
history but have never put it in pen form. I am not lucky enough to
work under a greybeard mentor who not only knows the electrical
aspects of audio, but also knows the reasons behind the way things are
done. As the older generation retires there is certainly lots of
knowledge that goes along with them.

ALL of this stuff is very thoroughly documented, much better than developments
today are being documented. Take a trip to a good college library and look
for old issues of the Bell System Technical Journal. Just about all of the
foundations of audio technology today can be found in there.

A couple years ago, in fact, I saw a paper on a new distortion mechanism
that a microphone manufacturer had discovered. Then I found a 1934 paper
in the BSTJ describing the same mechanism....
--scott
--
"C'est un Nagra. C'est suisse, et tres, tres precis."

[Scott Dorsey]

David Ballinger wrote:

Yes I have a gray beard, Nobody here remembers when telephone poles had
cross arms with green or clear glass insulators, yes open wire pairs, multi
pair cable hadn't been perfected yet, the last few places that used open
wire were the railroads for signals and com. the phone company started
frequency multiplexing on open wire lines 12 channels on 2 pairs just in
time for WWII. we have come a long way in a short time, not everybody had
telephones back then usually the rich and the Doctor and the sheriff, had 8
party lines too. Very few trunk lines between cities, it would take hours
to set up a long distance call, some of the little companies didn't talk to
each other at all. It wasn't exactly ladder line but the wires were
stretched tight enough they never crossed and stayed equidistant,
occasionally there would be a mid span cross-over device to minimize
crosstalk on the multiplex.

I hate to say it, but there are places in the world where it is still
like this. I had a guy call me from Burkina Faso with a Nagra problem
last year, and calling him back was just like making a long distance call
most of a century ago, with a dozen operators on the line at the time,
chatting away as they waited for the operator at the end of the line to
complete the circuit to the next station along the way. Then I got to
the village telephone and they sent out a runner to get the guy. MCI
decided to charge me for all the call setup time too.
--scott
--
"C'est un Nagra. C'est suisse, et tres, tres precis."

[George M. Middius[_4_]]

Scott Dorsey said:

I'm not sure I understand what a "nontechnical audio audience" is. Audio
is necessarily a technical field.

I'm not sure you understand what music is.

[Ben Bradley[_2_]]

(crossposting removed)


Newsgroups: rec.audio.pro,rec.audio.opinion,rec.audio.tubes,al t.feminazis
...
X-Complaints-To:

Woops, the faker added crossposting here, and it got a few RAP
responses - watch where your responses are going, folks!

(no further comments neccesary to this branch of the thread)

On Mon, 25 May 2009 18:54:00 +1000, Soundhaspriority
wrote:

snipped

[[email protected]]

On 26 Mai, 09:34, (Scott Dorsey) wrote:
In article ,

wrote:
Anyone who goes this far with a nontechnical audio audience is
showing off how big and thick his dick is. It is not necessary to
really understand transmission line theory in audio (unless you are
the phone company). Explaining the principle of common vs.
differential mode is enough.

I'm not sure I understand what a "nontechnical audio audience" is. *Audio
is necessarily a technical field.
--scott
--


It is not a field, it is a hobby.
the primary hobby is music, audio is secondary

[Mr.T]

"Scott Dorsey" wrote in message
...
A couple years ago, in fact, I saw a paper on a new distortion mechanism
that a microphone manufacturer had discovered. Then I found a 1934 paper
in the BSTJ describing the same mechanism....

And that's probably where they "discovered" it!
Common practice for manufacturers to not mention "minor" details like that
when they have products to promote.

MrT.

[[email protected]]

On May 26, 12:27*am, isw wrote:
The precise answer is around 37 ohms

I like that: kinda like saying it's exactly approximately.

[Scott Dorsey]

In article ,
wrote:
On 26 Mai, 09:34, (Scott Dorsey) wrote:
In article .=
com,

wrote:
Anyone who goes this far with a nontechnical audio audience is
showing off how big and thick his dick is. It is not necessary to
really understand transmission line theory in audio (unless you are
the phone company). Explaining the principle of common vs.
differential mode is enough.

I'm not sure I understand what a "nontechnical audio audience" is. =A0Aud=
io
is necessarily a technical field.

It is not a field, it is a hobby.

Strange, I thought people were actually making money doing audio work. Do
I have to give it all back?

the primary hobby is music, audio is secondary

Audio and music are related but by no means the same thing. Hell, lots of
people do plenty of fine audio work that involves no music at all, just
dialogue and talking head stuff.
--scott
--
"C'est un Nagra. C'est suisse, et tres, tres precis."

[Richard Crowley]

"Scott Dorsey" wrote ...
wrote:
It is not a field, it is a hobby.

Strange, I thought people were actually making money doing audio work. Do
I have to give it all back?

Scott, I think you are right. Hardly anything cross-posted from
another newsgroup (and especially r.a.o) is worthy of reading,
much less replying to.

[Serge Auckland[_2_]]

wrote in message
...
On May 26, 12:27 am, isw wrote:
The precise answer is around 37 ohms

I like that: kinda like saying it's exactly approximately.


Or very unique, or one of the only...sort of thing that makes me cringe when
I hear it on TV News.

S.
--
http://audiopages.googlepages.com

[Ron Capik[_2_]]

Serge Auckland wrote:

wrote in message
...
On May 26, 12:27 am, isw wrote:
The precise answer is around 37 ohms

I like that: kinda like saying it's exactly approximately.


Or very unique, or one of the only...sort of thing that makes me cringe
when I hear it on TV News.

S.
....and we all know the value can be up to 37 ohms or more. ;-)
[cringe away]



Later...

Ron Capik
--

[George M. Middius[_4_]]

Scott Dorsey said:

It is not a field, it is a hobby.

Strange, I thought people were actually making money doing audio work. Do
I have to give it all back?

Depends. Which commercial recordings were you responsible for?

[[email protected]]

Actually, what is amazing about all this is that it was all started by
a cross-posted troll.

Peter Wieck
Melrose Park, PA

[David Nebenzahl]

On 5/27/2009 8:22 AM Serge Auckland spake thus:

wrote in message
...

On May 26, 12:27 am, isw wrote:

The precise answer is around 37 ohms

I like that: kinda like saying it's exactly approximately.

Or very unique, or one of the only...sort of thing that makes me cringe when
I hear it on TV News.

"Very unique" irritates me too. Like saying someone is "sort of pregnant".

You either is or you isn't.


--
Found--the gene that causes belief in genetic determinism

[[email protected]]

On 27 Mai, 14:13, " wrote:
Actually, what is amazing about all this is that it was all started by
a cross-posted troll.

Peter Wieck
Melrose Park, PA

Isn't there supposed to be a big explosion'when the universe and anti-
universe meet?